The .22LR may have a greater "shock" effect to set off and displace C02 from the liquid if you cut the tip of the projectile flat, like a wadcutter.
Place the bottle's bottom towards you to give your bullet more distance-through-fluid to transfer energy into the carbonated water.
Bright red food dye to simulate the oxygenated blood of a lung shot. Hmm - maybe best leave that one till kids are older.
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